I can't find a way to 'consolidate' my projects.
When you import new Movie files and want to get rid of the old ones, you have to do it manually.?
Everything 'Transcoded' by Encore is also lying in the Sources and Cache folders.
How can I get rid of all the extra fat easily?
You can't easily do it: Encore doesn't offer any project consolidation tools.
To delete a video file, delete it from the Encore project, and then delete it from your system.
BTW, if you are working with a version of Encore earlier than 2.0, I recommend that you only delete transcoded files when you have completed the project. Encore 2.0 is a bit less fussy about missing transcodes than version 1.x.
Finally, if you don't need to re-author the project using the same assets, then just build a DVD image of your project. This will allow you to delete everything else about the project and still be able to burn a DVD from the image.